7: Molecular Genetics I - Molecular Biology of Gene Expression
- Page ID
- 146367
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Thus far, we've explored how phenotypic traits -- monogenic and complex -- are passed from one generation to the next via heritable changes in genetic material. However, we haven't given much thought to mechanistically how a gene is expressed as a trait. Doing so requires adopting an explicitly molecular genetic approach, where "genes" are sequences of DNA encoding proteins -- they are transcribed to make messenger RNA, which is translated to make a polypeptide, which folds into a functional protein. And proteins are the "do"ers of the cell -- molecular machines that do chemistry, transmit information, transform energy, etc. That means that proteins and their functions are directly responsible for an organism's phenotype.
Understanding how cells express genes -- the molecular basis of transcription and translation -- is important for two reasons. First, "how does genotype become phenotype" is a central question in the study of genetics. And second, a solid understanding of transcription and translation is important so we can subsequently consider how cells change when, where and how much a gene is expressed. That will be the subject of the next chapter.
Upon mastering the material in this chapter, you should be able to:
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Describe how transcription is initiated and terminated in prokaryotes and eukaryotes
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Predict how mutations in non-coding sequences affect gene expression
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Describe mRNA processing in eukaryotes
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Describe how tRNAs are used as “adapter” molecules
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Explain how the wobble hypothesis explains how 61 codons are translated with only 40 tRNAs